生物炭负载羧甲基纤维素钠稳定化纳米铁对水中六价铬的去除

利用液相还原法,通过先负载再包裹的方式制备了4种不同炭铁质量比的生物炭负载羧甲基纤维素钠稳定化纳米铁(BC-nZVI-CMC)材料,并将其用于对水中Cr(Ⅵ)的去除,使用扫描电镜、X射线衍射和傅里叶红外等技术对BC-nZVI-CMC的结构与性质进行了表征。结果表明：BC-nZVI-CMC具有较好的分散性,粒径为纳米级且被CMC完全包覆,抗氧化能力得到较大提升,可有效去除水中Cr(Ⅵ);投加1 g·L⁻¹的BC-nZVI-CMC对含有30 mg·L⁻¹的Cr(Ⅵ)去除率达99.83%;pH越小,越有利于BC-nZVI-CMC对水中Cr(Ⅵ)的去除,最高去除率可达100%;BC-nZVI-CMC的抗氧化能力明显高于商品纳米铁和生物炭负载纳米铁;含有8 g·L⁻¹ C/Fe=1∶1的BC-nZVI-CMC对电镀废水中Ni、Zn、Cu、总铬、Cr(Ⅵ)的去除率可达39.60%、91.70%、100%、91.69%、100%。上述研究结果对水中Cr(Ⅵ)去除新技术的开发有重要的参考价值。     

Performance evaluation of granular iron for removing hexavalent chromium under different geochemical conditions

Long-term column experiments were conducted under different geochemical conditions to estimate the longevity of Fe 0 permeable reactive barriers (PRBs) treating hexavalent chromium (Cr(VI)). Secondary carbonate minerals were precipitated, and their effects on the performance, such as differences in the mechanism for Cr removal and the changes in system hydraulics, were assessed. Sequestration of Cr(VI) occurred primarily by precipitation of Fe(III)-Cr(III) (oxy)hydroxides. Trace amounts of Cr were observed in iron hydroxy carbonate presumably due to substitution of Cr3+ for Fe3+. The formation of Fe(III)-Cr(III) (oxy)hydroxide greatly decreased the reactivity of the Fe 0 and thus resulted in migration of the Cr removal front. Carbonate minerals did not appear to contribute to further passivation with regard to reactivity toward Cr removal; rather, the column receiving high contents of dissolved calcium carbonate showed slightly enhanced Cr removal by means of a higher corrosion rate of Fe 0 and because of sequestration by an iron hydroxy carbonate. Precipitation of carbonates, however, governed other geochemical parameters. The porosity and hydraulic conductivity in the column receiving high contents of dissolved calcium carbonate did not indicate a great loss in system permeability because the accumulation of carbonates declined as the Fe 0 was passivated over time. However, the accumulated carbonates and associated Fe(III)-Cr(III) (oxy)hydroxide could cause problems because the presence of these solids resulted in a decline in flow rate after about 1400 pore volumes of operation.     

改性天然菱铁矿去除水中六价铬

六价铬Cr(Ⅵ)是地下水污染的重要组分之一。近几年吸附法除铬被广泛应用。为了强化Cr(Ⅵ)的去除效率,对成本低廉的天然菱铁矿进行了改性,并研究了最优改性条件及其对Cr(Ⅵ)的吸附特性。经过不同温度的灼烧改性发现,在500℃灼烧20 min时改性材料去除地下水中Cr(Ⅵ)的效率最高,在25℃时其吸附容量可达0.092 mg/g,吸附效率为92%。通过一系列的静态批实验,考察了最优改性菱铁矿对水中Cr(Ⅵ)的吸附效果。结果表明,二级吸附动力学模型可以更好地描述不同温度下的吸附过程。与Langmuir等温吸附模型相比,等温吸附数据更好地符合Freundlich等温吸附模型。溶液pH对改性天然菱铁矿的吸附效果影响较大,pH在2~8之间吸附容量基本稳定;当pH=8~11时,随着pH升高吸附量明显减小。SEM、比表面积、ZPC测定等结果表明,改性菱铁矿比表面积增大,pHzpc在7.8左右。因此,比表面积、表面电荷的分布等表面性质是改性天然菱铁矿除铬性能强的主要原因。     

Preparation of a novel iron-based biochar composite for removal of hexavalent chromium in water

The chitosan-stabilized ferrous sulfide nanoparticles were loaded on biochar to prepare a composite material FeS-CS-BC for effective removal of hexavalent chromium in water. BC and FeS-CS-BC were characterized by Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analyses. Batch experiments were employed to evaluate the Cr(VI) removal performance. The experimental results showed that the removal rate of Cr(VI) by FeS-CS-BC(FeS:CS:BC?=?2:2:1) reached 98.34%, which was significantly higher than that of BC (44.58%) and FeS (79.91%). In the pH range of 2–10, the removal of Cr(VI) by FeS-CS-BC was almost independent of pH. The limitation of coexisting anions (Cl^?、SO₄^2?、NO₃^?) on Cr(VI) removal was not too obvious. The removal of Cr(VI) by FeS-CS-BC was fitted with the pseudo-second-order dynamics, which was a hybrid chemical-adsorption reaction. The X-ray photoelectron spectroscopy (XPS) analysis result showed that Cr(VI) was reduced, and the reduced Cr(VI) was fixed on the surface of the material in the form of Cr(VI)–Fe(III).

Removal of hexavalent chromium from wastewater by FeS-CS-BC composite synthesized by impregnation.

     

Removal of hexavalent chromium of contaminated soil by coupling electrokinetic remediation and permeable reactive biobarriers

Purpose

In this study, a novel and ecological alternative have been developed to treat soils contaminated with hexavalent chromium coupling two well-known systems: electrokinetic remediation and permeable reactive biobarriers. The electric field promotes the electromigration of the hexavalent chromium oxyanions towards the anode. The biobarriers were placed before the anode electrode, in order to promote the reduction and retention of the chromium migrating in its direction. Thus, this technology provided a global treatment to soil removal without subsequent treatments of the contaminated effluents.

Methods

The electrokinetic system was coupled with two different permeable reactive biobarriers composed by Arthrobacter viscosus bacteria, supported either in activated carbon or zeolite. An electric field of 10?V was applied and two different treatment times of 9 and 18?days were tested.

Results

Removal values of 60% and 79% were obtained when electrokinetic treatment was coupled with zeolite and activated carbon biobarriers, respectively, for a test period of 18?day. The reduction of hexavalent chromium to trivalent chromium was around 45% for both systems.

Conclusions

In this work, two types of biobarriers were efficiently coupled to electrokinetic treatment to decontaminate soil with Cr(VI). Furthermore, the viability of the new coupling technology developed (electrokinetic?+?biobarriers) to treat low-permeability polluted soils was demonstrated.     

还原剂作用下Cr(Ⅵ)污染土渗透淋滤特性及成分分析

以湖南某铬污染场地中典型污染土壤为对象,采用硫酸亚铁(FeSO₄)和多硫化钙(CaS_x)2种还原剂,开展土壤修复实验和渗透淋滤实验,探讨不同还原剂对铬污染土渗透淋滤特性的影响规律,利用BCR形态提取和X射线衍射分析方法,评估不同还原剂对铬污染土中Cr(VI)的还原效果。结果表明,FeSO₄修复试样的渗透系数随FeSO₄/Cr(Ⅵ)摩尔比的增加呈先增加后降低的趋势,CaS_x修复试样的渗透系数变化呈现相反规律。相同条件下,FeSO₄修复试样的渗透系数较CaS_x修复试样的渗透系数更大,表明CaS_x修复试样的抗渗效果更好。随着还原剂掺量增加,修复试样渗出液中Cr(Ⅵ)浓度随之降低,当FeSO₄/Cr(Ⅵ)摩尔比大于3时,渗出液中Cr(Ⅵ)浓度低于Ⅲ类地下水标准Cr(Ⅵ)浓度基准值0.05mg·L⁻¹。类似地,当CaS_x/Cr(Ⅵ)摩尔比大于3时,淋滤实验后期渗出液Cr(Ⅵ)浓度也降至0.05 mg·L⁻¹以下。修复土中铬的赋存形态随还原剂掺量的增大而发生变化,铬由弱酸提取态向可还原态和可氧化态转化,且还原剂摩尔比也会对修复土壤组成成分产生影响。本研究结果可为Cr(Ⅵ)污染场地土壤修复工程提供参考。     

Fenton活化制备污泥炭对水中Cr (Ⅵ)的吸附性能

利用Fenton活化法活化脱水污泥制备活性炭,研究了Fenton试剂投加量、活化时间、炭化温度、炭化时间和升温速率5种因素对制备污泥炭的影响。污泥炭的最佳制备工艺：Fenton试剂投加量为150 mL,活化时间为2.5 h,炭化温度为350℃,炭化时间为1 h,升温速率为20℃·min-1。污泥炭碘吸附值达到331.90 mg·g-1,BET比表面积为24.265 m2·g-1。总孔容为0.146 cm3·g-1,微孔率为17%。分析了吸附时间、pH值和吸附温度3种因素对污泥炭吸附水中Cr（Ⅵ）的影响。在吸附时间为90 min,pH=3,吸附温度为50℃时,污泥炭对Cr（Ⅵ）的吸附量为9.93 mg·g-1。吸附动力学符合准二级动力学模型描述,吸附过程符合Langmuir和Tempkin等温吸附模型描述。     

Characterization of adsorbent composition in co-removal of hexavalent chromium with copper precipitation

Mechanisms of hexavalent chromium co-removal with copper precipitation by dosing Na2CO3 were studied with a series of well-designed batch tests using solutions containing 150 mg l-1 Cu(II) and 60 mg l-1 Cr(VI). It was found that direct precipitation of chromium through formation of copper-chromium bearing precipitates (in the form of CuCrO4) was one of the main mechanisms contributing to chromium co-removal at pH close to 5.0, and adsorption of chromium at a higher pH by freshly formed copper-carbonate precipitates (adsorbent) contributed to further chromium co-removal. Since, according to solubility products, neither copper-carbonate nor copper-hydroxide precipitates can be produced at pH around 5.0 for a pure 150 mg l-1 copper precipitation, characterization of copper-carbonate precipitates (adsorbent) was carried out through developing pC-pH curves of the systems by both equilibrium calculations and MINEQL+ 4.5 (a chemical equilibrium modeling software), and also through laboratory determination of the precipitate composition, such as gravimetric analyses, inorganic carbon percentage and EDAX spectrum analyses. CuCO3.Cu(OH)2, or a combination of CuCO3.Cu(OH)2 (in majority) and Cu(OH)2 (in minority) were suggested to be the major constituent of the precipitates obtained from the copper solution with Na2CO3 dosing.     

高价铬及双酚A在铁-乳酸体系中的同时光处理

研究了Fe(Ⅲ)-乳酸配合物体系同时对Cr(Ⅵ)的光还原及双酚A(BPA)的光氧化处理,考察了光源、初始pH值、Fe(Ⅲ)、乳酸盐、Cr(Ⅵ)及BPA初始浓度等因素对Cr(Ⅵ)及BPA光处理效率的影响。结果表明:光照条件下,铁-乳酸配合物能有效实现对六价铬及BPA的同时光处理。同一体系中,Cr(Ⅵ)的光还原快于BPA的光氧化,Fe(Ⅲ)初始浓度的增加可同时提高Cr(Ⅵ)的光还原效率和BPA的光氧化效率;Fe(Ⅲ)-乳酸盐配合物光解产生的Fe(Ⅱ)是Cr(Ⅵ)的主要还原剂,其次级光反应中产生的.OH是BPA的氧化剂。     

Kinetics of the reduction of hexavalent chromium with the brown seaweed Ecklonia biomass

The dead biomass of the brown seaweed, Ecklonia sp., is capable of reducing toxic Cr(VI) into less toxic or nontoxic Cr(III). However, little is known about the mechanism of Cr(VI) reduction by the biomass. The objective of this work was to develop a kinetic model for Cr(VI) biosorption, for supporting our mechanism. The reduction rate of Cr(VI) increased with increasing total chromate concentration, [Cr(VI)], and equivalent concentration of organic compounds, [OCs], and decreasing solution pH. It was found that the reduction rate of Cr(VI) was proportional to [Cr(VI)] and [OCs], suggesting the simple kinetic equation -d[Cr(VI)]/dt=k[Cr(VI)][OCs]. When considering the consumption of organic compounds due to the oxidation by Cr(VI), an average rate coefficient of 9.33 (+/-0.65)microM(-1)h(-1) was determined, at pH 2. Although the function of the pH could not be expressed in a mechanistic manner, an empirical model able to describe the pH dependence was obtained. It is expected that the developed rate equation could likely be used for design and performance predictions of biosorption processes for treating chromate wastewaters.     

The styrene purification performance of biotrickling filter with toluene-styrene acclimatization under acidic conditions

The obvious disadvantages of biotrickling filters (BTFs) are the long start-up time and low removal efficiency (RE) when treating refractory hydrophobic volatile organic compounds (VOCs), which limits its industrial application. It is worthwhile to investigate how to reduce the start-up period of the BTF for treating hydrophobic VOCs. Here, we present the first study to evaluate the strategy of toluene induction combined with toluene-styrene synchronous acclimatization during start-up in a laboratory-scale BTF inoculated with activated sludge for styrene removal, as well as the effects of styrene inlet concentration (0.279 to 2.659 g·m^?3), empty bed residence time (EBRT) (i.e., 136, 90, 68, 45, 34 sec), humidity (7.7% to 88.9%), and pH (i.e., 4, 3, 2.5, 2) on the performance of the BTF system. The experiments were carried out under acidic conditions (pH 4.5) to make fungi dominant in the BTF. The start-up period for styrene in the BTF was shortened to about 28 days. A maximum elimination capacity (EC_max) of 126 g·m^?3·hr^?1 with an RE of 80% was attained when styrene inlet loading rate (ILR) was below 180 g·m^?3·hr^?1. The highest styrene RE(s) [of BTF] that could be achieved were 95% and 93.4%, respectively, for humidity of 7.7% and at pH 2. A single dominant fungal strain was isolated and identified as Candida palmioleophila strain MA-M11 based on the 26S ribosomal RNA gene. Overall, the styrene induction with the toluene-styrene synchronous acclimatization could markedly reduce the start-up period and enhance the RE of styrene. The BTF dominated by fungi exhibited good performance under low pH and humidity and great potential in treating styrene with higher inlet concentrations.

Implications: The application of the toluene induction combined with toluene-styrene synchronous acclimatization demonstrated to be a promising approach for the highly efficient removal of styrene. The toluene induction can accelerate biofilm formation, and the adaptability of microorganisms to styrene can be improved rapidly by the toluene-styrene synchronous acclimatization. The integrated application of two technologies can shorten the start-up period of biotrickling filters markedly and promote its industrial application.     

化学还原固定化土壤地下水中六价铬的研究进展

化学还原法在受铬污染土壤地下水系统修复过程中应用广泛。化学还原固定化方法通过将溶解度大、迁移性强的六价铬(Cr(VI))还原转化为稳定的三价铬(Cr(III))氢氧化物,从而实现铬污染控制与修复的目的。常用的还原剂包括:含铁类还原剂(零价铁、纳米零价铁和亚铁类还原剂)、还原性硫化物(H2S、Fe Sx、硫代硫酸盐和多硫化合物等)及一些具有还原活性的有机物。本文系统地综述了不同还原剂对六价铬还原固定化的机理、影响因素、修复效果及适用范围;重点对常用还原剂的优缺点进行了比较,并提出了存在的问题和今后的发展方向。     

Formation of organic tracers for isoprene SOA under acidic conditions

The chemical compositions of a series of secondary organic aerosol (SOA) samples, formed by irradiating mixtures of isoprene and NO in a smog chamber in the absence or presence of acidic aerosols, were analyzed using derivatization-based GC–MS methods. In addition to the known isoprene photooxidation products 2-methylglyceric acid, 2-methylthreitol, and 2-methylerythritol, three other peaks of note were detected: one of these was consistent with a silylated-derivative of sulfuric acid, while the remaining two were other oxidized organic compounds detected only when acidic aerosol was present. These two oxidation products were also detected in field samples, and their presence was found to be dependent on both the apparent degree of aerosol acidity as well as the availability of isoprene aerosol. The average concentrations of the sum of these two compounds in the ambient PM_2.5 samples ranged from below the GC–MS detection limit during periods when the isoprene emission rate or apparent acidity were low to approximately 200 ng m^?3 (calibrations being based on a surrogate compound) during periods of high isoprene emissions. These compounds presently unidentified have the potential to serve as organic tracers of isoprene SOA formed exclusively in the presence of acidic aerosol and may also be useful in assessments in determining the importance and impact of aerosol acidity on ambient SOA formation.     

锰掺杂硫化锌量子点LED蓝光灯光催化还原六价铬

通过共沉淀法合成了锰掺杂硫化锌量子点(ZnS∶Mn QDs),该催化剂可在450 nm LED蓝光灯下光催化还原Cr(Ⅵ)。采用TEM、XRD、PL分别对ZnS∶Mn QDs的形貌、物相和发光特性进行了表征,结果表明：ZnS∶Mn QDs的尺寸小于10 nm;Mn掺杂没有改变ZnS的晶体结构;ZnS在掺杂Mn后,可在598 nm处产生橘黄色荧光。UV-vis表征结果显示,与纯ZnS相比,ZnS∶Mn QDs具有更强的光吸收能力。考察了不同因素对光催化效果的影响。结果表明,Mn掺杂浓度3%较为合适,酸性pH有利于光催化反应。当Cr(Ⅵ)浓度为25 mg·L⁻¹,pH为5.8时,光催化25 min后Cr(Ⅵ)去除率为99%。与其他光催化剂还原Cr(Ⅵ)相比,ZnS: Mn QDs使用低能耗LED灯作为光源,催化速率高,且能够吸附还原产物Cr(Ⅲ)。探究了光催化机理,发现在450 nm光激发下,Mn²⁺自身能级⁴T₁→⁶A₁发生跃迁产生光生电子,Cr(Ⅵ)捕获光生电子被还原,价带上余留的空穴参与水的氧化。结合表征结果,ZnS可通过掺杂Mn离子改善光吸收能力提高光催化还原Cr(Ⅵ)的性能。     

一株耐铬产碱菌的鉴定及其铬(Ⅵ)解毒特性

为了将微生物更好地应用于治理环境污染,从长期Cr(Ⅵ)污染区域筛选Cr(Ⅵ) 耐受细菌,并研究其去除Cr(Ⅵ)的特性。结果表明:筛选出1株产碱菌CQMU-1能高效除去培养体系中的Cr(Ⅵ),用于去除环境中Cr(Ⅵ)污染是可行的。7种细菌中菌株CQMU-1的Cr(Ⅵ) 耐受能力最强,经鉴定为粪产碱菌;当初始Cr(Ⅵ)浓度为100 mg/L、pH为6.0~8.0、温度为30℃、接种细菌浓度为0.5~2.0 g/L时,CQMU-1的Cr(Ⅵ)去除率最高,达94.6%;培养120 h后,培养液中Cr(Ⅵ)明显减少,总Cr无显著变化,菌体中Cr含量极少。     

Rapid reductive dechlorination of atrazine by zero-valent iron under acidic conditions

The dechlorination of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) via reaction with metallic iron under low-oxygen conditions was studied using reaction mixture pH values of 2.0, 3.0, and 3.8. The pH control was achieved through addition of sulfuric acid throughout the duration of the reaction. The lower the pH of the reaction mixture, the faster the degradation of atrazine. The surface area of the sulfuric acid-treated iron particles was 0.31 (+/- 0.01) m2 g-1 and the surface area normalized initial pseudo-first order rate constants (kSA, where rate = kSA x (surface area/l) x [Atrazine]) at pH values of 2.0, 3.0, and 3.8 were equal to, respectively, 3.0 (+/- 0.4) x 10(-3) min-1 m-2 l, 5 (+/- 3) x 10(-4) min-1 m-2 l, and 1 (+/- 1) x 10(-4) min-1 m-2 l. The observed products of the degradation reaction were dechlorinated atrazine (2-ethylamino-4-isopropylamino-1,3,5-triazine) and possibly hydroxyatrazine (2-ethylamino-4-isopropylamino-6-hydroxy-s-triazine). Triazine ring protonation may account, at least in part, for the observed effect of pH on atrazine dechlorination via metallic iron.     

Enhanced removal of toxic hexavalent chromium from aqueous solution by magnetic Zr-MOF@polypyrrole: performance and mechanism

Environmental Science and Pollution Research - Magnetic Zr–based metal organic framework (UiO-66) @Polypyrrole (magnetic UiO-66@Ppy) was prepared to eliminate Cr(VI) from water. SEM and TEM...     

Leaching behavior and chemical stability of copper butyl xanthate complex under acidic conditions

Although xanthate addition can be used for treating copper-containing wastewater, a better understanding of the leaching toxicity and the stability characteristics of the copper xanthate complexes formed is essential. This work was undertaken to evaluate the leaching behavior of copper xanthate complex precipitates by means of toxicity characteristics leaching procedure (TCLP) and semi-dynamic leaching test (SDLT) using 1 N acetic acid solution as the leachant. Also, the chemical stability of the copper xanthate complex during extraction has been examined with the studying of variation of chemical structure using UV-vis, Fourier transform infrared and X-ray photoelectron spectroscopies (XPS).Both TCLP and SDLT results showed that a negligible amount of copper ion was leached out from the copper xanthate complex precipitate, indicating that the complex exhibited a high degree of copper leaching stability under acidic conditions. Nevertheless, chemical structure of the copper xanthate complex precipitate varied during the leaching tests. XPS data suggested that the copper xanthate complex initially contained both cupric and cuprous xanthate, but the unstable cupric xanthate change to the cuprous form after acid extraction, indicating the cuprous xanthate to be the final stabilizing structure. Despite that, the changes of chemical structure did not induce the rapid leaching of copper from the copper xanthate complex.     

粉煤灰复合氧化钙去除铬渣渗滤液中的总铬

粉煤灰虽然具有较大的比表面积,但单独做为处理剂处理含铬废水,效果并不理想,具有吸附容量小、溶解损失大、且有毒性浸出等特点.为了解决粉煤灰以上缺陷,提出氧化钙复合粉煤灰去除铬渣渗滤液中总铬的技术,研究表明,在室温25℃条件下,总铬初始浓度在0.30~80.00 mg/L范围内,选择粉煤灰与CaO配比为1:1时,以150 r/min转速充分振荡24 h,总铬去除率均能达到90%以上.通过空白对照实验研究表明,粉煤灰复合CaO使用,对总铬的去除远优于单独使用粉煤灰或CaO做为吸附剂的处理效果.利用SEM,XRD,红外光谱分析3种材料表征方法,对粉煤灰原料、CaO-粉煤灰处理后残渣等进行分析,结果表明,在水介质条件下,粉煤灰与CaO能生成晶体矿物.当溶液中有铬存在时,晶体矿物在形成的过程中能将铬裹入其结构中.通过浸出实验表明,此晶体矿物对铬具有很好的固定作用.     

Trivalent chromium solubility and its influence on quantification of hexavalent chromium in ambient particulate matter using EPA method 6800

Measurement of carcinogenic Cr(VI) in ambient PM is challenging due to potential errors associated with conversion between Cr(VI) (a carcinogen) and Cr(III) (an essential nutrient). Cr(III) conversion is a particular concern due to its >80% atomic abundance in total Cr. U.S. Environmental Protection Agency (EPA) method 6800 that uses water-soluble isotope spikes can be used to correct the interconversion. However, whether the enriched Cr(III) isotope spikes can adequately mimic the Cr(III) species originally in ambient PM is unknown. This study examined the water solubility of Cr(III) in ambient PM and discussed its influence on Cr(VI) measurement. Ambient PM₁₀ samples were collected on Teflon filters at four sites in New Jersey that may have different Cr emission sources. The samples were ultrasonically extracted with 5 mL DI-H₂O (pH 5.7) at room temperature for 40 min, and then analyzed by ion chromatography–inductively coupled plasma mass spectrometry (IC-ICPMS). Cr(III) was below detection limit (0.06 ng/m³) for all samples, suggesting water-soluble Cr(III) species, such as CrCl₃, Cr(NO₃)₃, and amorphous Cr(OH)₃, in the ambient PM were negligible. Therefore, the enriched ⁵⁰Cr(III) isotope spike (in the form of Cr(NO₃)₃) could not mimic the original ambient Cr(III). Only the conversion of ⁵³Cr(VI) (in the form of K₂CrO₄) was taken into account when correcting the interconversion. We then used NaHCO₃-pretreated MCE filters (prespiked with enriched isotope species) to measure Cr(VI) in the ambient PM₁₀. The samples were ultrasonically extracted at 60 C pH 9 solutions for 40 min followed by IC-ICPMS analysis. Due to the correction of Cr(VI) reduction, the Cr(VI) concentrations determined by EPA method 6800, 0.26 ± 0.16 (summer) and 0.16 ± 0.11(winter) ng/m³ (n = 64), were significantly greater than those by the external standard curve, 0.21 ± 0.17 (summer) and 0.10 ± 0.07 (winter) ng/m³ (n = 56) (p < 0.01, Student’s t-test). Our study revealed that appropriate application of EPA method 6800 is important because it only applies to soluble fraction of Cr species in ambient PM.

ImplicationsAccurate measurement of carcinogenic Cr(VI) in ambient PM is challenging due to conversion between Cr(VI) (a human carcinogen) and Cr(III) (a human essential nutrient). The conversion of Cr(III) is of particular concern due to its dominant presence in total Cr (>80%). This study examined the water solubility of Cr(III) in ambient PM that was collected at four locations in New Jersey. Then we discussed the influence of Cr(III) solubility on the application of EPA method 6800, which utilizes enriched isotope spikes to correct the interconversion. Our results suggested that appropriate application of EPA method 6800 is important because it only applies to soluble fraction of Cr species.